Spatial patterns of grapevines with Pierces disease in the lower San Joaquin valley

• Author(s): Bartels, David; Civerolo, Ed; Hashim, Jennifer; Tubajika, Kayimbi;
• Abstract: Incidence of Pierces disease (PD, caused by Xylella fastidiosa), continues to increase in many grape varieties in California due to the establishment and spread of the vector, the glassy-winged sharpshooter. Eleven vineyards were surveyed during 2001 season and each vine was assessed visually for PD and Geo-referenced using GPS/GIS technology. The spatial patterns of infected vines were analyzed by ordinary runs and two-dimensional distance class analyses, and illustrated using multispectral images. Disease incidence ranged from 1% to 80%. No disease gradient or edge effect was detected in any vineyard. The spatial disease gradient analyses consistently described the non-randomness of the patterns of diseased vines, and an increase in the degree of clustering of diseased vines as disease incidence increased. Based on these results, effective PD management is likely to be based on practices that reduce initial inoculum and use of resistant varieties.
• Publication Date: Jun 2002
• Journal: Phytopathology